Multi-Particle%20Azimuthal%20Correlations%20at%20RHIC%20!!

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Multi-Particle Azimuthal Correlations at RHIC !!
What do they tell us about Possible Quenching?
Roy A. Lacey USB - Chem (SUNY Stony Brook)
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Outline

• Motivation
• General
• Specific
• Correlation Technique
• Assorted-pT method
• Fixed-pT method
• Advantages of the Methods
• Correlation Results
• - Compatible with Jets, Flow, etc. ?
• - What have we learned ?

See W. Holzmans Poster
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The Big Picture
Motivation - General
What can we learn from experiments about this
past history?
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Motivation - Why Study Correlations
Correlation Studies can provide information on
the particle production mechanism,the EOS,
Initial State effects, QGP formation. (Very
Important Signal)
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Reminder - Single Particle Distributions
Au Au Experiment
d Au Control Experiment
Preliminary Data
Final Data

• Striking difference between dAu and AuAu
  results.
• Cronin effect dominate in dAu
• High-pT Jet Suppression dominate in AuAu.

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The Problem
B. Muller nucl-th/0208038
Extreme Quenching not Sufficient to Account
for Observed Npart Dependence of V2
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Measuring Azimuthal Correlations
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Constructing Correlation Functions
Wang et al., PRC 44, 1091 (1991) Lacey et al.
PRL 70, 1224 (1993)
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Approach - 1
Definition
Azimuthal Distributions and Correlation
Functions are Characterized by an Anisotropy and
an Asymmetry.
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Information in Correlation Functions
HIJING
Hydro or Transport With large Opacity
Flow leads to strong anisotropy no asymmetry
Jets lead to strong anisotropy and an asymmetry

• The anisotropy of the correlation function can
  reflect
• both flow and Jet contribution
• The Asymmetry provides crucial Jet Information

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Extracting v2 via Fixed Correlations
v2 characterize the Anisotropy
pT
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Extracting v2 via Assorted Correlations
pT
Reference
pT
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dAu Assorted-pT Correlation Functions
Di-jet structure develops with increasing pT
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Comparison of dAu and AuAu
Peripheral AuAu is essentially identical dAu
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Comparison of dAu and AuAu
Apparent away-side suppression
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Comparison of dAu and AuAu
Mid-Central events indicate sizeable harmonic
contributions
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Comparison of 130 and 200 GeV Results
PHENIX Preliminary
Anisotropy (v2) essentially identical
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Differential v2
Minimum Bias
Model performance depend on pT range ?
All models Require Humongous Energy Densities
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Centrality Dependence of v2

• Different Models predict different scaling
• behavior for the centrality dependence of v2
• Hydro/Molnar --- eccentricity scaling
• Minijet Overlap Area scaling

eccentricity
y
x
It is important to test for these different
scaling behavior !
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Centrality Dependence Compatible with Npart
scaling scaling
Scaling compatible with quenching and Flow
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v2 pT Scaling
High and low pT charged hadrons show similar
scaling Common denominator ?
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v2 Scaling
v2 Centrality Scaling
Molnar et al.
V2 Scaling observed in models
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v2 centrality Scaling
00-05
Preliminary
Two Different scaling patterns are obtained
--- Respective dominance of Jets and flow-like
contributions
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Reference Range Dependence
v2 does not show significant dependence on pTRef
Very Important --- v2(rxpln) v2(corr)
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Assorted Correlation Functions for pp AuAu

• Asymmetry of Correlation
• function sensitive to
• pTRef
• Charge Selection
• Consistent with presence of
• Jets

Jets correlated with Reaction plane
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Summary/Picture
Jets are correlated with the Reaction Plane due
to Quenching
then thermalized matter expands From pressure
build up -gt elliptic flow -gt v2
Jet-quenching early Jets remember geometry (-gt
v2)
Consistent picture for quenching, v2, jets